CN105207270B - Improve the inverter power control method for coordinating of grid-connected voltage out-of-limit - Google Patents
Improve the inverter power control method for coordinating of grid-connected voltage out-of-limit Download PDFInfo
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- CN105207270B CN105207270B CN201510766067.0A CN201510766067A CN105207270B CN 105207270 B CN105207270 B CN 105207270B CN 201510766067 A CN201510766067 A CN 201510766067A CN 105207270 B CN105207270 B CN 105207270B
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- 238000010248 power generation Methods 0.000 description 6
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
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Abstract
The invention discloses a kind of inverter power control method for coordinating for improving grid-connected voltage out-of-limit, it is related to the device or method technical field for adjusting electric variable.Methods described comprises the following steps：1) the voltage U at grid entry point is detected in photovoltaic combining inverter operation in real timeS, the upper voltage limit U at grid-connected pointmaxFor known quantity；If 2) US≤UmaxWhen, inverter sends active-power P with MPPT control modelsPV；If 3) US＞ UmaxWhen, inverter startup power coordination control model, grid entry point voltage is maintained upper voltage limit UmaxPlace.Methods described can make the voltage real-time response grid entry point voltage change that photovoltaic DC-to-AC converter exports, the active power and reactive power of dynamically distributes photovoltaic DC-to-AC converter, ensure that grid-connected voltage maintains its upper limit or following all the time, inverter number out of service is reduced, photovoltaic generation is possessed notable, flexible pressure regulation ability.
Description
Technical Field
The invention relates to the technical field of devices or methods for adjusting electric variables, in particular to a reactive power adjustment control method for an inverter, which can prevent photovoltaic grid-connected voltage from exceeding the limit.
Background
With the increasingly prominent energy crisis problem, renewable energy is more popular to people, especially solar energy which is clean, pollution-free, wide in resource distribution and convenient to exploit. Photovoltaic power generation is rapidly increasing worldwide as a form of efficient use of solar energy. The photovoltaic grid connection can be directly connected to the grid at the low-voltage side or connected to the grid after passing through a step-up transformer. After the photovoltaic power supply is incorporated into the power distribution network, the original single-power radial structure is changed into a multi-power structure, the original trend direction and size are changed, and the photovoltaic grid connection has larger and larger influence on the voltage of the power distribution network along with the improvement of the photovoltaic permeability. The problem that the grid-connected point voltage is out of limit after photovoltaic grid connection needs to be solved. The main technical means for improving the voltage out-of-limit of the power distribution network in the prior art are as follows: the technical means of the method comprise on-load voltage regulation of a transformer, capacitor bank compensation, active filter (APF) compensation, static Var Generator (SVG) compensation and the like, the hardware investment needs to be increased, and the method is not suitable for all power distribution networks connected with photovoltaic.
Disclosure of Invention
The invention aims to solve the technical problem of providing an inverter reactive power regulation control method for preventing photovoltaic grid-connected voltage from exceeding the limit, which can enable the voltage output by a photovoltaic inverter to respond to the voltage change of a grid-connected point in real time, dynamically distribute the active power and the reactive power of the photovoltaic inverter, ensure that the voltage of the photovoltaic grid-connected point is always maintained at the upper limit or below, reduce the operation exit frequency of the inverter and enable the photovoltaic power generation to have obvious and flexible voltage regulation capability.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the method for coordinately controlling the power of the inverter for improving the out-of-limit of the photovoltaic grid-connected voltage is characterized by comprising the following steps of:
1) Real-time detection of voltage U at grid-connected point during operation of photovoltaic grid-connected inverter S Upper voltage limit U at grid-connected photovoltaic point max Is a known amount;
2) If U is S ≤U max The inverter sends out active power P in an MPPT control mode PV ；
3) If U is S ＞U max In time, the inverter starts a power coordination control mode to maintain the voltage of a grid connection point at an upper voltage limit U max To (3).
The further technical scheme is as follows: the power coordination control mode specifically includes the following steps:
if U is S ＞U max In time, the inverter starts a power coordination control mode and records the active power P sent by the current inverter PV Reactive power Q 'from the inverter at this time' PV Is composed of
Active power P generated by the inverter PV And the reactive power Q 'generated by the inverter obtained by the calculation of the formula (1)' PV The PQ control is carried out on the inverter as active power and reactive power reference input values at the next moment of the inverter;
detecting inversion at the next timeGrid-connected point voltage U S If the voltage does not exceed the upper voltage limit U of the photovoltaic grid-connected point max The inverter keeps running in the current mode, and in the process, if the active power P sent by the current inverter is in the current mode PV And if the output power is increased continuously, the emitted reactive power Q 'is reduced according to the formula (1)' PV ；
If the voltage of the grid-connected point U S Still exceeds the upper voltage limit U of the photovoltaic grid-connected point max At this time, the active power P emitted by the inverter is reduced PV Simultaneously increasing the emitted reactive power Q 'according to the formula (1)' PV ；
When Q' PV When the voltage is no longer negative, namely when the inverter is required to really send out reactive power, if the voltage of a grid connection point is higher, the sent out active power P is only reduced PV To maintain the voltage of the grid-connected point at the upper voltage limit U max To (3).
The further technical scheme is as follows: the inverter can utilize reactive power of
When Q is PV When the voltage is more than 0, the inverter sends out reactive power, and the voltage of a grid connection point is increased, so that the inverter can absorb the reactive power, namely, send out negative reactive power
Will present P PV And Q 'calculated from formula (3)' PV And PQ control is carried out on the inverter as active and reactive power reference input values at the next moment of the inverter.
The further technical scheme is as follows: active power reduction delta P of inverter PV The determination method of (2) is as follows:
active power P emitted by inverter PV Reactive power Q PV Active power P consumed by load L Reactive power Q L Satisfy the following relationships
In formula (4): r is a line resistance connected to the photovoltaic power supply, X is a line reactance connected to the photovoltaic power supply, U O Is the distribution network voltage;
from formula (4):
(U O -U S )U S ＝(P L -P PV )R+(Q L -Q PV )X (5)
after the power coordination control mode is started, if the voltage U of the grid-connected point is the voltage U S The more the upper limit is still, the active power P is sent out from the inverter PV Next, in order to reduce the voltage of the grid-connected point to the upper voltage limit U max Active power P 'that the inverter should emit' PV Satisfy the requirement of
(U O -U max )U max ＝(P L -P′ PV )R+(Q L -Q PV )X (6)
The active power reduction delta P of the inverter obtained by the joint type (5) and the formula (6) PV Is composed of
Active power P 'that the inverter should emit' PV Is composed of
P′ PV ＝P PV +ΔP PV (8)
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: according to the method, the problem that the voltage at the grid-connected point is out of limit can be effectively solved only by adjusting the reactive power and the active power value input by the photovoltaic grid-connected inverter, so that the voltage at the grid-connected point is always kept at or below the upper limit of the voltage of the photovoltaic grid-connected point, no additional hardware is needed, the cost is low, the control principle is simple, the number of times that the inverter exits from operation can be effectively reduced, the photovoltaic power generation has obvious and flexible voltage regulation capacity, the photovoltaic grid-connected performance is improved, and the photovoltaic power generation and the power distribution network can effectively operate.
Drawings
FIG. 1 is a diagram of a single grid-tied photovoltaic access distribution network system architecture;
wherein: 1. photovoltaic module 2, inverter 3, distribution network.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.
The invention discloses an inverter power coordination control method for improving photovoltaic grid-connected voltage out-of-limit, which can effectively solve the problem of voltage out-of-limit at a grid-connected point by only regulating reactive power and active power value input by a photovoltaic grid-connected inverter, so that the voltage at the grid-connected point is always maintained at the upper limit or below the voltage of the photovoltaic grid-connected point, no additional hardware is needed, the cost is low, the control principle is simple, the number of times that the inverter exits from operation can be effectively reduced, the photovoltaic power generation has obvious and flexible voltage regulation capability, the photovoltaic grid-connected performance is improved, and the photovoltaic power generation and a power distribution network can effectively operate.
Starting the inverter for grid connection, and operating in an MPPT control mode at the initial operation stage of the inverter, namely only emitting active power P PV . Inverter real-time detection grid-connected point voltage U S And recording the currently emitted active power P PV And reactive power Q PV (when no reactive power is emitted, Q PV Is 0). Distribution network voltage U O Line reactance X connected with photovoltaic power supply and upper voltage limit U at photovoltaic grid-connected point max In known amounts.
(1) If U is S ≤U max And the inverter sends out active power in an MPPT control mode.
(2) If U is S ＞U max In time, the inverter starts a power coordination control mode and records the active power P sent by the current inverter PV . In the normal case, P PV ＜S PV So that the reactive power available for the inverter can be obtained as
When Q is PV When the voltage is more than 0, the inverter sends out reactive power, and the voltage of a grid connection point is increased more, so that the inverter can absorb the reactive power, namely, negative reactive power is sent out.
Will present P PV And Q 'calculated from formula (1)' PV And PQ control is carried out on the inverter as active and reactive power reference input values at the next moment of the inverter.
And detecting the voltage of the grid-connected point of the inverter at the next moment, and if the voltage does not exceed the upper limit of the voltage, keeping the inverter running in the current mode. In the process, if the active power P PV And increasing continuously, reducing the emitted reactive power according to the formula (1).
If the voltage of the grid-connected point is higher, the emitted active power P is reduced PV While increasing the reactive power emitted according to equation (1).
When Q' PV When no longer negative, i.e. requiring inversionWhen the converter emits reactive power, if the voltage of the grid connection point is higher than the upper limit, only the emitted active power P is reduced PV 。
Active power P PV Decrease amount of (Δ P) PV Is determined by:
the inverter sends out active power P PV Reactive power Q PV Active power P consumed by load L Reactive power Q L Satisfy the following relationships
From the formula (3)
(U O -U S )U S ＝(P L -P PV )R+(Q L -Q PV )X (4)
When the power coordination control mode is started, if the voltage of a grid connection point still exceeds the upper limit, the active power P is sent out from the inverter PV To lower the grid-connected point voltage to the upper voltage limit U max Active power P 'that the inverter should emit' PV Satisfy the requirements of
(U O -U max )U max ＝(P L -P′ PV )R+(Q L -Q PV )X (5)
The reduction of active power of the inverter obtained by the joint type (4) and the formula (5) is
Active power P 'that the inverter should emit' PV Is composed of
P′ PV ＝P PV +ΔP PV (7)
Wherein, U O For distribution network voltage, U S Is the voltage of the grid-connected point, R is the line resistance connected with the photovoltaic power supply, X is the line reactance connected with the photovoltaic power supply, S PV Injecting capacity, P, into a distribution grid for photovoltaics PV For photovoltaic alignmentActive power Q generated by power grid PV Reactive power, P, to the distribution network for photovoltaic L Active power, Q, consumed for the load L Reactive power consumed for the load.
Claims (1)
1. The inverter power coordination control method for improving photovoltaic grid-connected voltage out-of-limit is characterized by comprising the following steps:
1) Voltage U at real-time detection grid-connected point during operation of photovoltaic grid-connected inverter S Upper voltage limit U at grid-connected photovoltaic point max Is a known amount;
2) If U is present S ≤U max The inverter sends out active power P in an MPPT control mode PV ；
3) If U is S >U max Then, the inverter starts a power coordination control mode to maintain the voltage of the grid-connected point at the upper voltage limit U max At least one of (1) and (b);
the power coordination control mode specifically includes the following steps:
if U is present S >U max In time, the inverter starts a power coordination control mode and records the active power P sent by the current inverter PV At this time, the reactive power Q 'emitted by the inverter' PV Is composed of
Active power P emitted by the inverter PV And the reactive power Q 'generated by the inverter obtained by the calculation of the formula (1)' PV The PQ control is carried out on the inverter as the active and reactive power reference input values at the next moment of the inverter; wherein S is PV Injecting capacity into the distribution network for the photovoltaic;
detecting the voltage U of the grid-connected point of the inverter at the next moment S If the voltage does not exceed the upper voltage limit U of the photovoltaic grid-connected point max The inverter keeps running in the current mode, and in the process, if the active power P sent by the current inverter is in the current mode PV Increasing is continued according to equation (1)) Reducing emitted reactive power Q' PV ；
If the voltage of the grid-connected point U S Still surpass the upper voltage limit U at the photovoltaic grid-connected point max At this time, the active power P emitted by the inverter is reduced PV Simultaneously increasing the emitted reactive power Q 'according to the formula (1)' PV ；
When Q' PV When the voltage of the grid-connected point is higher than the upper limit of the voltage, the active power is only reduced, so that the voltage of the grid-connected point is maintained at the upper limit of the voltage U max At least one of (1) and (b);
the inverter can utilize reactive power of
When Q is PV &0, the inverter sends out reactive power, and the voltage of the grid connection point is increased, so that the inverter can absorb the reactive power, namely, send out negative reactive power
Will present P PV And Q 'calculated from formula (3)' PV The PQ control is carried out on the inverter as active power and reactive power reference input values at the next moment of the inverter;
active power reduction delta P of inverter PV The determination method of (2) is as follows:
active power P emitted by inverter PV Reactive power Q PV Active power P consumed by load L And reactive power Q L Satisfy the following relationships
In formula (4): r is the line resistance connected to the photovoltaic power supply, X is the line reactance connected to the photovoltaic power supply, U O Is prepared byThe grid voltage;
from formula (4):
(U O -U S )U S ＝(P L -P PV )R+(Q L -Q PV )X (5)
after the power coordination control mode is started, if the voltage U of the grid-connected point is the voltage U S The more the upper limit is still, the active power P is sent out from the inverter PV To lower the grid-connected point voltage to the upper voltage limit U max Active power P 'that the inverter should emit' PV Satisfy the requirements of
(U O -U max )U max ＝(P L -P′ PV )R+(Q L -Q PV )X (6)
Active power reduction delta P of inverter obtained by combining vertical type (5) and formula (6) PV Is composed of
Active power P 'that the inverter should emit' PV Is composed of
P′ PV ＝P PV +ΔP PV (8)。
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| CN107437822B (en) * | 2017-10-09 | 2020-01-03 | 太原理工大学 | Photovoltaic grid-connected inverter control method for preventing voltage of low-voltage distribution network from exceeding limit |
| CN110086421B (en) * | 2019-05-06 | 2021-01-08 | 阳光电源股份有限公司 | Intelligent photovoltaic module and photovoltaic power generation system |
| CN114123218B (en) * | 2021-11-24 | 2024-02-02 | 国网山东省电力公司电力科学研究院 | Overvoltage layering and partitioning suppression method for distribution network at distributed photovoltaic access terminal |
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| CN104079007A (en) * | 2014-03-06 | 2014-10-01 | 西安理工大学 | Distributed grid-connected photovoltaic power generation control method for inhibiting overvoltage of low-voltage feeder line |
| CN104767221A (en) * | 2015-04-21 | 2015-07-08 | 国家电网公司 | Voltage regulation method based on inverter power coordination control |
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